(1) Field of the Invention
The present invention relates generally to engine coolant/antifreeze, and more particularly the present invention relates to an engine coolant which comprises water soluble salts of succinic acid, water soluble salts of acetic acid, ethanol, and water.
(2) Description of Related Art
Many chemicals can achieve a freezing point depression greater than that of an aqueous solution. The freezing point depression of an antifreeze solution is a function of the properties of the chemical and the concentration of the chemical in the solution.
U.S. Pat. No. 4,448,702 to Kaes teaches lowering the freezing point of an aqueous system by adding a freezing point lowering quantity of water soluble salts of dicarboxylic acids having at least three carbon atoms, such as sodium, potassium, ammonium or organoamine salts of adipic, glutaric, succinic and malonic acids.
U.S. Pat. No. 5,876,621 to Sapienza teaches a deicing composition comprising hydroxycarboxylic acid esters or sugar compounds. Sapienza further teaches a method of preparing a deicing composition by recovering from an industrial waste stream hydroxycarboxylic acids, which are then alcoholized to convert the hydroxycarboxylic acids to hydroxycarboxylic acid esters.
U.S. Pat. No. 5,980,774 to Sapienza teaches a water soluble deicing composition comprising freezing point lowering compounds such as hydroxycarboxylic acid esters, glycosides and mixtures thereof. Sapienza further teaches methods of use, and preparation of such compounds by recovering from an industrial waste stream hydroxycarboxylic acids, and adding freezing point lowering compounds such as hydroxycarboxylic acid esters, glycosides and mixtures thereof.
U.S. Pat. No. 6,129,857 to Sapienza teaches a deicing and/or anti-icing composition comprising at least 15 weight percent of sorbitol and water and methods of deicing by applying the compositions. The deicing composition can further include freezing point lowering additives such as hydroxycarboxylic acid salts, acetate salts, formate salts, citrate salts, amino acids and salts of amino acids, dicarboxylic acid salts, lignin components, boric acid and boric acid salts, glycerol, and mixtures thereof.
U.S. Pat. No. 6,156,226 to Klyosov teaches liquid and solid de-icing and anti-icing agents comprising neutral or alkaline, non-chloride, non-phosphate and non-glycol compositions. The liquid compositions are based upon aqueous solutions of organic acid salts such as lactic acid, succinic acid, acetic acid, and formic acid salts. The solid compositions comprise organic-based porous pulp and paper sludge granules impregnated with the liquid de-icing composition. The liquid compositions can be obtained either by direct mixing of commercially available chemicals, by chemical transformation of commercially available acids, or by fermentation of sugars.
U.S. Pat. No. 6,287,480 to Berglund teaches deicing compositions which are suitable and effective for airport applications in which corrosion of magnesium based alloys is an issue. The deicing compositions are less corrosive upon steel and aluminum and certain magnesium based parts than conventional road salt. The compositions also inhibit the corrosive effects of conventional road salt. The deicing compositions include succinate salts, such as potassium succinate (trihydrate), ammonium succinate (anhydrous), sodium succinate (hexahydrate), either alone or in combination. Additionally, the deicing compositions include corrosion inhibiting, deicing amounts of potassium succinate together with 1) polymaleimide sodium salt and magnesium succinate, 2) magnesium succinate and sodium polyaspartate, 3) sodium polysuccinimide, 4) sodium polyaspartate and polymaleimide sodium salt, or 5) magnesium succinate.
U.S. Pat. No. 6,506,318 to Sapienza teaches deicing and anti-icing compositions comprised of hydroxyl-containing organic compounds and/or organic acid salts and methods of deicing and anti-icing using the compositions.
Antifreezes have a broad category of uses including use as deicing compounds which are typically applied at airports and roadways. These deicing compounds are usually solid and are applied to surfaces for the purpose of melting ice. They are also anti-icing in that they dissolve into any water which comes in contact with the surface, thereby lowering its freezing point and inhibiting ice build up.
Antifreezes also include the category of automobile engine coolants, which have unique characteristics in addition to preventing freezing. Engine coolants are necessarily liquids which have good heat transfer properties for cooling an engine during use, while also having antifreeze properties to prevent freezing when the engine is not active in cold weather. The engine coolants must be able to perform at high temperatures under pressure for extended times, as well as very cold temperatures. Engine coolant/antifreeze must also be non-corrosive to engine components. The performance of engine coolant/antifreeze solutions is governed by the American Society for Testing and Materials (A.S.T.M.) and the Society of Automotive Engineers (S.A.E.). The most widespread antifreeze presently used as an engine coolant consists of ethylene glycol.
Ethylene glycol is synthesized by the oxidation of ethylene in the presence of acetic acid producing ethylene diacetate, which is then hydrolyzed to the glycol. Ethylene glycol (1,2 ethanediol) has excellent performance properties, however it also has some undesirable properties. The U.S. Department of Health and Human Services and the U.S. Environmental Protection Agency have determined that ethylene glycol is acutely toxic to humans and animals. Also, the rate of biodegradation of glycols is an environmental concern considering the volume of engine coolant in use and the likelihood of leakage into the soil and waterways.
Propylene glycol (1,2 propanediol) is used as an alternative to ethylene glycol due to its decreased toxicity, however there is still a demand to replace glycols used in engine coolants with more environmentally friendly and non-toxic alternatives. Any replacement engine coolant/antifreeze must have adequate antifreeze and cooling capacities. Another important consideration with any engine coolant/antifreeze is the corrosion which it causes within an engine, and the chemical interactions of the coolant with hose and gasket elastomers. Oxidation products of ethylene glycol include formic acid and glycolic acid. The corrosive properties of a coolant and its oxidation products can destroy components of the engine. Since this corrosiveness can lead to failure of the engine, any replacement engine coolant/antifreeze should have low corrosivity.
While related art antifreezes all decrease the freezing point of aqueous solutions to some extent, there is still a need to develop liquid antifreeze solutions which have performance properties that are required in an engine coolant/antifreeze. Additionally, there is a need to develop an engine coolant/antifreeze produced from non-toxic renewable resources. Therefore, it would be desirable to have a high-performance engine coolant/antifreeze which is produced from renewable resources that are biodegradable, non-toxic, and non-corrosive to engines.